Vulnerability · Published Jun 26, 2026 · Assigned by GitHub_M

CVE-2026-47775Envoy OAuth2 Filter: Padding Oracle via AES-256-CBC Cookie Decryption

Medium 6.8

In plain English

A medium-severity broken cryptography in envoy from envoyproxy. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 12% of all known vulnerabilities).

Severity (CVSS 3.1)6.8Medium

Exploit odds (30 days)0.2%top 87.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, the OAuth2 HTTP filter's encrypt()/decrypt() functions use AES-256-CBC without an authentication tag (no HMAC, no AEAD). The /callback endpoint returns HTTP 302 on successful decryption and HTTP 401 on padding failure, creating a padding oracle. An attacker who obtains the encrypted CodeVerifier cookie can recover the plaintext PKCE code_verifier in ~6,200 requests (~100 seconds), then exchange it with a stolen authorization code to obtain the victim's access token. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.

Affected products (as reported)

Vendor	Product	Versions
envoyproxy	envoy	>= 1.38.0, < 1.38.1>= 1.37.0, < 1.37.3>= 1.36.0, < 1.36.7< 1.35.11

Weakness: CWE-209, CWE-327 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

References

https://github.com/envoyproxy/envoy/security/advisories/GHSA-396h-jpq4-vc7p x_refsource_CONFIRM